class Solution {
    public int tribonacci(int n) {
        if(n<=0)
        return 0;
        if(n==1||n==2)
        return 1;
        int dp[]=new int[n+1];
        dp[0]=0;
        dp[1]=1;
        dp[2]=1;
        for(int i=3;i<=n;i++){
        dp[i]=dp[i-1]+dp[i-2]+dp[i-3];
        }
        return dp[n];
        
    }
}
